Wireless networks are gaining popularity to its peak today, as the users want wireless operates without the use of external infrastructure. But the proliferation of such MANET based connectivity irrespective of their geographic position. MANETs are best suited for emergency situations as they facilitate fully distributed, self-maintainable dynamic topology networks that applications are limited as its features impart high applicability, yet they manifest unreliability. Another cause of

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... lity is the mutual intrinsic trust during communication. One such attack exploiting this trustworthiness is called the Black Hole attack wherein the Black Hole in the network promises routing of the data packet to the destination while in actuality it drops them hence decreasing reliability. Black hole attack is one of the security threats in which the traffic is redirected to such a node that actually does not exist in the network. It's an analogy to the black hole in the universe in which things disappear. The node presents itself in such a way to the node that it can attack other nodes and networks knowing that it has the shortest path. MANETs must have a secure way for transmission and communication which is quite challenging and vital issue. The aim of this paper is to detect and prevent the effects of Black hole attack in MANET using Reactive routing protocol like Ad-Hoc on Demand Distance Vector (AODV) and analyse MANETs under single and collaborative Black Hole attack and prevent it by diverting traffic from the Black Hole. The proposed method is based on sending confirmation packets that are verified by the destination to check for Black Hole presence in the proposed AODV routing protocol and encrypt the data before sending it to destination. The proposed AODV algorithm was then simulated in static node environment and it was observed that its data delivery ratio is significantly better than the conventional AODV.